• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.756-759
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• 2001

The purpose of this paper is to investigate the buckling and dynamic characteristics for the cylindrical shell under shear loading. To do this, a vibration model tests and analyses and static buckling analyses were performed for the reduced scale model of nuclear reactor vessel. From the results of vibration modal analysis with the pre-shear displacement loads, it is known that the beam vibration mode is not affected by the shear displacement, however shell vibration modes are significantly affected by it. As the pre-shear displacement increases to the critical buckling displacement, the 1st shell vibration frequency in greatly reduces and approaches to zero value.

• Journal of Korean Association for Spatial Structures
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• v.13 no.3
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• pp.65-72
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• 2013

Long span arch structure is composed of arch as relatively flexible structure and column as relatively rigid structure. In this study, the characteristic of dynamic response is analyzed according to the natural frequency ratio between arch and columns. The result of analysis for arch as relatively vertical vibration mode is dominant, the influence of columns mainly appears at relatively high frequency band according to increase of 1st mode frequency in column. However, the dynamic characteristic of arch structure is expected to vary with not only frequency ratio but interaction between vibration modes of arch and columns.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.110-112
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• 2003

A numerical simulation of an incompressible cavity flow is conducted using turbulence models. Cavity geometry and flow conditions are based on Cattafesta's experiment. Baldwin-Lomax model and ${\kappa}-{\varpi}$ model are employed. While simulation with Baldwin-Lomax model predicts the oscillatory features of the flow, the use of ${\kappa}-{\varpi}$ model in its original form makes the simulation converge to steady flow. To acquire oscillatory flow solution, Kato-Launder form and Time scale bound are adopted in production term of ${\kappa}-{\varpi}$ model. The strouhal number of the flow oscillations from the simulation results corresponds to 1 st mode in simulation but 2 nd mode in experiments. However mean velocity profile is in good agreement with the experimental data and the fluctuation profile follows the tendency of Cattafesta's results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1871-1874
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• 2000

It is impossible to predict accurately the dynamic behavior of turbine-generator system because bearing, and rotor characteristics are nonlinear and different from temperature, load, operation speed and bearing lubricant oil property. Especially, the characteristics of turbine hoods affect much the entire vibration characteristics of turbine. As the dynamic stiffness of turbine hoods are changed, the critical speeds of rotor are shifted. In this paper, the vibration behavior of turbine-generator is analyzed by using component mode synthesis and the critical speeds measured during shut-down are compared with the analytic results. It is confirmed that the 1st natural frequency and the mode shape are well in agreement with actual measured data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.854-855
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• 2013

As an unique acoustic characteristic of a Korean bell. beat phenomenon is a periodic repetition of strong and weak sounds. Beat sounds good when it is clear and it has a proper period, however, it is not easy to satisfy these two conditions simultaneously. In this study, we propose a beat tuning method to satisfy these two conditions, by using an equivalent bell model. First, we construct an equivalent bell which has the same beat property with the 1st beat of a real bell and we investigate the change of mode pair by finite element analysis, when thickness of the bell is locally decreased at $22.5^{\circ}$ from the striking point. From the analysis result, minimum thickness reduction amount is determined to make a clear and strong beat.

• Journal of Korean Society of Disaster and Security
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• v.7 no.1
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• pp.43-50
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• 2014

Based on the reliability theory, the risk assessment of steel beams is performed by the determination of failure probability. In the calculation, bending, shearing and combined (bending + shearing) modes are examined. The resistance and the loads on the beam are assumed to be normal distribution. To investigate the failure probability changes, total load applied at the mid span of beam is divided into 1 to 1 and 1 to 2 ratio and then these divided loads are placed on the trisected points on beam. The change of boundary conditions at beam ends are also included in the investigation. It shows that failure is governed by the combined mode for the present beams and the second order bound analysis of failure probability is not crucial. On the whole failure probability decreases with increasing end restraints at the beam ends with some exception.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.3
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• pp.56-64
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• 2013

The wind resistant capacity of bridges with a span of less than 200m is typically evaluated by Wind Resistant Design Manual for Highway Bridges in Japan. Also, the first vertical frequency plays an important role in the evaluation of their aerodynamic performance. An unexpected vortex-induced vibration of Nielsen arch bridge with span of 183m designed by this manual has been measured by monitoring system during typhoon. The amplitude of vibrations was about 2 times than the allowable vibration displacement. This paper presents the feature of vortex-induced vibration of this Nielsen arch bridge based on measured wind velocity, wind direction, and responses at midspan of main girder. From the result of FFT, the $1^{st}$ mode shape of the bridge is antisymmetric and the $2^{nd}$ is symmetric. Also, the dominant vibration of the bridge is the $2^{nd}$ vertical mode. According to these results, the $2^{nd}$ vertical vibration mode of this Nielsen arch bridge is prior to the first for the estimation of wind resistance capacity.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.10
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• pp.1114-1122
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• 2005

This research investigates the effects of sonication mode, reaction temperature and volume on sonolysis of 1,4-dioxane in order to increase the degradation efficiency and kinetics. The degradation efficiency in case with pulse mode was about 10 % higher than that in case with continuous mode. The degradation profiles in both cases, which were performed without the control of reaction temperature and in 1000 mL, were composed of three steps. However, 1,4-D was mainly degraded in the initiation step as the first portion and the acceleration step as the second portion. The initial step agreed with zero-order expression well, while the acceleration step could be fitted with pseudo 1st-order expression. The kinetic model in case with $5^{\circ}C$ and 300 mL conformed to pseudo 1st-order, while that in cases with $10^{\circ}C$ to $40^{\circ}C$ agreed with zero-order expression. The degradation efficiency and profile of 1,4-D in the experiment with $20^{\circ}C$ and 300 mL was higher and simpler than that in case with $20^{\circ}C$ and 1000 mL. The reaction temperature and volume influence bubble intensity, which was produced in sonication. The increase of bubble intensity induced to augment the production of OH radical in sonication.

• Journal of Korean Association for Spatial Structures
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• v.14 no.1
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• pp.77-84
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• 2014

Simple 3, 10, and 30-story buildings with a nonstructural element which is located at roof or near the middle of the building height are selected. Based on 2009 Korean Building Code, the seismic design force applied at the nonstructural element is evaluated. Response spectrum analysis is conducted with the design response acceleration spectrum of 2009 Korean Building Code and the analytical response is compared with the seismic design force from the Code. Furthermore, an artificial earthquake based on Korean design response acceleration spectrum and the 50% intensity of El Centro earthquake, which can be considered as the maximum future earthquake possibly occurring in Korea, are selected to conduct time history analysis. When the period of the nonstructural element is shorter than 0.06 second or longer than that of the 1st period of each building, the Code equations of seismic design force for nonstructural element seems to be appropriate. However, the period of the nonstructural element is close to the one of the building's higher mode periods including the 1st period, seismic force of the nonstructural element might exceed the Code specified seismic design force.

• Mass Spectrometry Letters
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• v.4 no.3
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• pp.55-58
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• 2013

Dioscin is a biologically active steroidal saponin with anticancer and hepatoprotective effects. A rapid, selective, and sensitive liquid chromatographic method with electrospray ionization tandem mass spectrometry was developed for the quantification of dioscin in rat plasma. Dioscin was extracted from rat plasma using ethyl acetate at acidic pH. The analytes were separated on a Halo C18 column using gradient elution of acetonitrile and 0.1% formic acid and detected by tandem mass spectrometry in selected reaction monitoring mode. The standard curve was linear ($r^2$ = 0.998) over the concentration range of 1-100 ng/mL. The lower limit of quantification was 1.0 ng/mL using 50 ${\mu}L$ of plasma sample. The coefficient of variation and relative error for intra- and inter-assay at four QC levels were 1.3 to 8.0% and -5.4 to 10.0%, respectively. This method was applied successfully to the pharmacokinetic study of dioscin after oral administration of dioscin at a dose of 29.2 mg/kg in male Sprague-Dawley rats.